The present invention relates to an integrated circuit for driving a d.c. motor with radio controller. The invention is particularly directed to an integrated circuit for operating a switching machanism of a d.c. motor having a forward-to-reverse bidirectional mode or a forward-to-reverse mode added to a latch function with the input signal controlled by radio.
In prior arts, there were various kinds of remote control methods for model cars such as shown in FIG. 1, FIG. 3 and FIG. 4.
FIG. 1 is a block diagram of a motor driving apparatus having only forward-to-reverse switching control, in which individual components are used. FIG. 2 is a concrete circuit diagram of FIG. 1.
A transmitter used in the remote control of model cars having a forward-to-reverse switching control has a non-modulated transmitting system having carrier frequency ranging from only 47 MHz to 49 MHz.
A super regenerative receiving circuit 1 in FIG. 1 or FIG. 2 generates a quenching frequency ranging from 100 KHz to 500 KHz. When there is not the transmitted signal from the said transmitter, said quenching signal is generated in the receiving circuit and a noise signal (20 Hz.about.10 KHz) is introduced to an antenna 11 and are mixed and fed to an amplifier 2 through a low pass filter composed of resistors R.sub.5, R.sub.6 and a capacitor C.sub.4. However, when there is a transmitted signal from the transmitter, only the quenching signal is introduced to the amplifier 2. The amplifier amplifies only the noise frequency and the rotational direction of a motor M becomes forward or reverse through a detector 3 and a relay 4.
Therefore, said d.c. motor driving circuit for a remote controlled model car is manufactured at high cost and has a large size due to individual transistors, diodes, resistors and relay etc.
FIG. 3 is a linear integrated circuit for driving a d.c. motor disclosed in U.S. Pat. No. 4,488,094 by the present applicant.
This device of FIG. 3 includes an amplifier 6 for amplifying the audio frequency, a peak detector 7 for converting the said amplified signal into the d.c. signal, a comparator 8 having a hysteresis character, a motor driving circuit 9 and a voltage regulated circuit 10. This device has only the forward-to-reverse switching control.
This device suffers from the disadvantage of requiring two separate batteries and continuously pushing a transmitter switch on the transmitter to change the rotational direction of motor.
FIG. 4 is a block diagram of a d.c. motor driving circuit having three functions of forward rotation, stop and reverse rotation like the present invention. This device includes an amplifier 13, and pass filters 14 for obtaining three other frequencies in accordance with each operationg mode, peak detectors 15 for converting the signals drawn out of band pass filters into d.c. signal, comparators 16 and motor driving circuit 17.
This device of FIG. 4 has the disadvantages of the complexity of a transmitting circuit and a receiving circuit and has low receiving sensitivity in comparison with the super regenerative receiving system generally used in a remote radio controlled model car.